Nice original driveshaft, pulled from a non-running early-model 260Z (prod. 11/73) with 4-speed transmission and R180 w/ curved mustache bar. Should fit other years with that drivetrain configuration, but can't guarantee that. U-joints still seem tight; no slop. Shaft and splines clean and undamaged. $80 plus shipping.
Thx for looking.

Yes, that would certainly work for you on a mild tune....GM has used single exhaust that size on many of their V8 applications over the years.
If if you wanted to build a little margin into the system for possible future upgrades (e.g. bigger cam, carb, etc), you could use 3" for the single pipe after the Y. This is what I'm running for my current exhaust with a mild Lunati cam and Holley 600.
My two cents, FWIW.

Not my ad, but a pretty good deal. Wish this had come up two years ago, before I bought my rust-bucket special.
https://www.facebook.com/marketplace/item/359481901480997
(Admins: if this is the wrong sub-forum to post this in, please feel free to delete and/or move. Thanks.)

Yeah.....the only way I'm aware for that is to use lengths of PVC pipe off the trans and the diff (pipe needs to be stiff enough to prevent bending or drooping under its own weight). Take measurements and calculate the side-to-side angle with geometry. As you already noted, that angle needs to be combined with the vertical angle to derive your compound angle. Good article here on that topic: http://www.ocdriveshaft.com/ShaftFacts/DrivelineVibration.aspx

There are unfortunately not nearly as many body kits and body styling parts for the S130 as there are for the S30. I am not aware of anyone that produces a rocket-bunny style kit for the 130. (Your car being a 2+2 may limit your choices even further.)
Retro-Spec is one of the few vendors that offers some parts for the ZX: https://retro-spec.myshopify.com/collections/datsun-280zx

Yes, completely feasible. And quite honestly, I think 1/8" would be overkill. IIRC, the entire shell is produced mostly with 16 and 18 gauge sheet (someone please chime in if I'm misstating).
For pictures of the mods described by Neverdone, check out Jon Mortensen's build. Several people have built tube front ends, but Jon's car is the only one that comes to mind at the moment. Folks have done all kinds of front end and frame mods to relocate the radiator and accommodate larger radiators, intercoolers, etc.

You are correct on all counts. I haven't seen any produced anytime recently. They will occasionally pop up for sale in used condition, but they are becoming extremely hard to find. Apparently, they are a bit more readily available in Japan than elsewhere....but not cheap. Some guys have fabricated their own custom hatches, which may account for the differences in style that you noted.
I'm fairly certain that molds still exist, so you might be able to have someone create a single hatch for you from a mold. Check out the discussion threads on ClassicZCar.com, and you might get some useful leads.
I personally like the look of the Pantera hatch, but not everyone does, as you've already noticed. Whatever you decide to do, good luck with it.

If there's enough thread to thread on two nuts, you tighten them together, then wrench on the inner nut to remove the stud. Otherwise, vise grips is probably the best non-welding solution, as suggested by the others. The

If you're on FB, Harold Burroughs has one for sale on "Datsun Parts and Needs".....don't recall if it's for a Series 1.
https://www.facebook.com/groups/TheZGang/?multi_permalinks=1934760669892395&notif_id=1543455023197491&notif_t=group_highlights

Here's another interesting option for LED headlights....anyone using these? Seems like a good price, and Silvermine is known for quality products.
https://www.silverminemotors.com/datsun/datsun-280z/body-parts/240z-260z-280z-led-headlight-low-beam-hi-beam-driving-light-blinker-sae-dot-compliant

Those are pretty aggressive offsets you're considering; so to answer your question....yes, they would certainly "fill" the flares; and could quite possibly exceed the flares, depending on your tire choice. Tire selection will be a big consideration obviously. Low aspect tires on the thin side obviously require way less clearance from the fenders & flares than wider rubber. There are other factors that will play a role as well: how much is the suspension lowered, how much neg camber are you running, etc, etc.
I would definitely invest in a wheel mockup tool to ensure your planned setup will work before dropping the change on new parts. You can even make your own measurement tool with some simple hardware.
Finally, you are aware that some DRW use differing lug tapers on their lug nut holes, I'm assuming? Using the wrong tapered lug nut can be a major safety issue.

I did it with my front bar, and am much happier with it than I was with the original mounting points embedded in the frame rails.
There's a couple of threads on this technique here on HybridZ.....I think maybe Jon Mortensen did a little write-up on it at one point? If you search, you should find them. (Hint: Google search works better than the website's organic search function....just be sure to include "HybridZ" in your search string.)
P.S. Looking at your pictures again, it appears that those welds don't really have much penetration....so another reason to not use those mounting points.

I personally would not use that. Would it fail during use? Depends on a whole host of factors.....what kind of usage, sway bar thickness, spring rates, what kind of tires, etc, etc. If all your driving is pleasure cruising on the streets, it's probably fine. If you're building a car for any serious kind of track use, then it's probably not fine. Don't know why a PO would do that unless the original mounting holes had become rusted out or stripped.
There's a technique to strengthen the sway bar mounts by sandwiching the entire frame rail with steel plates and running long bolts all the way through the frame rail (from top to bottom) to provide the mounting points. You need to run correctly-sized steel tubes through the frame rails to ensure that the long bolts don't crunch the frame rails when tightening.
Good luck with it.